The present invention relates generally to pumping devices and particularly to a pumping device having limited moving mechanical parts.
All pumps of whatever type are subject to mechanical wear. In the case of a recirculating pump, where the outlet fluid eventually returns to the inlet, a rotary gear pump has been generally used. Because it is a constant volume pump, it should be sized according to the expected fluid demand. A recirculating pump is especially vulnerable to any dirt or debris in the fluid. Further, a recirculating pump is not easily movable because of the required driving unit used in conjunction with a recirculating pump. The driving unit, mechanical coupling, and recirculating pump itself all combine to reduce reliability and increase maintenance costs. A recirculating pump is usually not expected to have a high delivery rate, but reliability is of the utmost importance. In particular, as used in oil drilling operations a recirculating pump must operate to maintain operation of the entire oil well. Once the recirculating pump fails, the entire oil well must be shut down for repair or replacement of the recirculating pump.
Air driven pumps have the liability of a mechanical shuttle arrangement built into the pump itself, and the shuttle arrangement is a typical cause for pump failure. The mechanical constraints of the shuttle valve often put a limit on pump configuration. Pump discharge pressure typically cannot be raised much without sacrificing output volume. Many air driven pumps also use a diaphragm along with the shuttle valve and this introduces an additional source of potential mechanical failure.